I tried to power an ESP32 naked board from the P1S internal USB cable the other day.
It failed.
The ESP32 board would not start or it got toasted?
I’m running an ESP32 board but from a dedicated power supply to capture the sensor data from several sensors connected to my ESP32 board. Power supplies are Best Buy store brand with adjustable outlet voltage. Noticed the ESP was scorching hot and Adafruit suggested lowering the voltage, which I did. Spec for board says 6V - 12V supply is acceptable but lowered it to 7V and board cooled right down.
I got a industrial type power strip and mounted it under the table that has 12 outlets because it was pretty sure that that on-board USB-B would nor support lights, sensors
Going off the rail:
The V-reg on most of ESP32 dev board, such as NodeMCU, is LDO regulator (linear type). It only work best without much loss if input is about 1.5V higher than output.
The thing with linear regulator is: it is analogy of voltage divider of 2 resistors
In layman’s terms, you want 3v3 from 12v using linear V-reg, you have to waste 8v7. Say, ESP32 takes 240mA from 3v3, you pretty much waste at least P_waste = 8v7 * 0.24A = 2.09w. It seems not much but it is enough to burn your finger if you touch a 2w heater.
Btw, I don’t trust the power from USB port on AP board. First of all, the wire coming from the PSU is not that thick. Secondly to step down from 24v safely, it should be buck regulator. And without post regulator, 5v output would be noisy.
The led strip mosfet in that size can only do 200mA upto 600mA. Same size of mosfet on x1c ap board.
From my memory, the LED strip from Aliexpress for X1C took 1.7A@5V when I did the power consumption test off my lab psu. I bought it to improve x1c lighting but never used it. That LED strip had correct connector which suppose to be direct replacement of built-in LED bar for controlling via bambu app.
It is truely wonder when some people used these Aliexpress led strip for x1c for weeks without burning something. And of course, a few paid the price for their lack of knowledge.
I use dedicated power supplies for anything I put on P1S.
LED lights have a 24V supply box that plugs into a power strip.
Metro Express ESP32-S2 plugs into another socket on power strip.
Nothing is tapped into the printer.
In regards to that USB port, I have a theory that the port exists not for the benefit of users. It exists for Bambu Labs testing or programming needs. There is some residual power available to support what Bambu uses it for (IMO)
Using the USB port on AP board is ok for running an ESP32 dev board. The regular buck v-reg in SOIC8 size can normally do 1A to 3A depends on manufacturer, so 1.5A spec written on the board is quite reasonable.
It’s just the voltage is noisy and having bad interfering with wifi activity of the ESP32 dev board you are running mostly.